None.
Not Applicable.
The present invention relates to vehicle service equipment such as is commonly utilized in vehicle repair shops, and more particularly, to improved vehicle service equipment such as wheel balancers and wheel alignment systems configured to utilize vehicle wheel lateral force measurements in the repair or adjustment of vehicle wheel and suspension systems.
The determination of unbalance in vehicle wheels, consisting of tires carried on a wheel rims, is carried out by an analysis with reference to the phase and amplitude of the mechanical vibrations caused by rotating unbalanced masses in the vehicle wheel. The mechanical vibrations are measured as motions, forces, or pressures by means of transducers, which convert the mechanical vibrations to electrical signals. Each signal is the combination of fundamental oscillations caused by imbalance and noise.
It is well known in the art that a variety of types of correction weights are available for placing on the vehicle wheel to correct the measured imbalance. For example, adhesive-backed weights, patch balance weights, and hammer-on weights are available from a number of different manufacturers.
Even when a vehicle wheel is balanced, non-uniformity in the construction of the tire as well as runout in the wheel rim can cause significant vibration forces as the wheel rolls under vehicle load. Most tire manufacturers inspect their tires on tire uniformity machines, such as disclosed in U.S. Pat. No. 6,116,084 to Fischer et al. To improve the rolling characteristics of non-uniform tires, it is common to grind rubber off the tread surface of the tires. Even after this procedure, tires will often produce vibration forces (not related to imbalance) of 20 pounds or more as they roll on a smooth road.
Some vehicle wheels develop forces in the lateral (or axial) direction when rolling straight ahead on a flat road. This condition may cause a vehicle to steer away from a straight line. Sources of lateral forces include tire conicity, ply steer, and the combination of the two, known as total lateral force. Tire conicity may be envisioned by considering a vehicle wheel to assume the shape of a truncated cone as it rolls. Based on geometry, such a configuration will always generate a force towards the apex of the cone regardless of the direction in which the vehicle wheel rotates. Thus, conicity is a force component which does not change direction with reverse rotation when measuring tire lateral residual forces. By definition:   Conicity  =                    TLF        CW            +              TLF        CCW              2  
where TLFCW is the total lateral force of the vehicle wheel measured in the clockwise direction, and TLFCCW is the total lateral force of the vehicle wheel measured in the counter-clockwise direction. Tire conicity is believed to be caused by the placement of internal tire components, such as belts off-center about the circumference of the tire, resulting in the tire having one sidewall which is stiffer than the other.
Tire ply steer lateral forces result from the influence of the plies in a tire in generating forces which can steer a vehicle from a straight line course. These forces are theorized to be related to the direction of the cords in the outermost ply, and hence, as the direction of rotation is reversed, the direction of the force generated by the outermost ply also changes. Thus tire ply steer is a force component which changes direction with reverse rotation when measuring tire lateral residual forces. By definition:   Plysteer  =                    TLF        CW            -              TLF        CCW              2  
where TLFCW is the total lateral force of the vehicle wheel measured in the clockwise direction, and TLFCCW is the total lateral force of the vehicle wheel measured in the counter-clockwise direction.
Other lateral forces which may be measured include the peak-to-peak lateral force variation, the lateral first harmonic force variation, as well as other higher lateral harmonic force variations.
The variations in radial and lateral forces during the rotation of a vehicle wheel are usually caused by differences in the stiffness and/or geometry of the vehicle wheel about its circumference or tread centerline. If these differences are slight, the radial and lateral force variations and therefore the degree of tire conicity will be insignificant and their effects unnoticeable when the vehicle wheel is installed on a vehicle. However, when these differences reach a certain level, the radial and/or lateral force variations may be significant enough to cause rough riding conditions and/or difficult handling situations. Furthermore, an excessive tire conicity value will cause a rolling tire to pull to one side.
Conditions such as tire conicity and ply steer cannot be corrected during the balancing of a vehicle wheel with the attachment of balancing weights. Temporary corrections to such conditions can be made by altering the shape of the vehicle wheel through the use of grinding machines and the remove of tire tread material from specifically identified regions on the vehicle wheel. Examples of such systems are shown in U.S. Pat. No. 3,948,004 to Gruber, U.S. Pat. No. 4,112,630 to Brown, Jr. and U.S. Pat. No. 5,645,465 to Vannan, III. However, such operations do not result in a long-term solution to the effects of lateral forces, and may result in shortened tire life as the remaining tire tread wears. Accordingly, there is a need in the industry to develop equipment capable of utilizing vehicle wheel lateral force measurements in the placement of vehicle wheels about a vehicle and in the adjustment of vehicle alignment components.
Briefly stated, a first embodiment of the present invention is a vehicle service system configured to utilize lateral force measurement information associated with a set of vehicle wheels to provide an operator with a suggested placement for the individual vehicle wheels about the vehicle, such that the effects on the vehicle handling caused by the lateral forces are minimized.
In a second embodiment of the present invention, a vehicle service system is configured to utilize lateral force measurement information associated with a set of vehicle wheels to provide an operator with one or more suggested adjustments to the vehicle suspension components, such that the effects on the vehicle handling caused by the lateral forces are minimized.
In a third embodiment of the present invention, a vehicle wheel balancer is provided, which includes a shaft adapted for receiving a vehicle wheel, a rotation sensor assembly for measuring rotation of the shaft about its longitudinal axis, and a motor operatively connected to the shaft for rotating the shaft about its longitudinal axis, thereby to rotate the vehicle wheel. At least one vibration sensor assembly is provided for measuring the vibration of the vehicle wheel as the vehicle wheel assembly is rotated. A load roller is provided which applies a predetermined generally radial force to the vehicle wheel. At least one force sensor is provided which measures forces exerted by the vehicle wheel in the lateral (axial) direction as the load roller is in contact with the vehicle wheel. A display is provided to present the operator with a visual indication of the measured vibrations and forces exerted by the vehicle wheel, which are stored in a memory, together with the measured vibrations and forces exerted by at least one addition vehicle wheel. A computer provides the operator with suggested placement locations about a vehicle for the vehicle wheels, based upon the stored measured vibrations and forces exerted by the vehicle wheels.
In a fourth embodiment, a vehicle wheel alignment system is provided, which includes at least one vehicle wheel alignment sensor configured to measure at least one vehicle wheel alignment angle, a computer configured to receive alignment measurement data from the vehicle wheel alignment sensor, and a display through which the computer provides measurement and adjustment information to an operator. The computer is further configured to receive lateral force measurement information for at least one vehicle wheel, and to utilize the received lateral force measurement information to suggest either a placement for the associated vehicle wheel, or an adjustment to the vehicle wheel alignment, which will compensate for at least a portion of the lateral force exerted by the associated vehicle wheel when the vehicle is in motion. The lateral force measurements may be input by the operator, received from a separate piece of automotive service equipment, or may be measured by the vehicle wheel alignment system.
The foregoing and other objects, features, and advantages of the invention as well as presently preferred embodiments thereof will become more apparent from the reading of the following description in connection with the accompanying drawings.